Communication system and method for improving efficiency and linearity

ABSTRACT

A communication system and method is provided that modifies a signal for transmission at a transmitter to reduce peaks associated with the signal. The signal can be modified employing signal shaping, signal clipping, signal decomposition or other techniques to remove peaks associated with the signal. The communication system can also correct the modified signal at a receiver to reconstruct the originally wanted signal.

TECHNICAL FIELD

The present invention relates generally to electronic devices, and moreparticularly to a system and method for improving efficiency andlinearity in communications.

BACKGROUND OF THE INVENTION

RF power amplifiers used for wireless communication transmitters, withspectrally efficient modulation formats, require high linearity topreserve modulation accuracy and to limit spectral regrowth and otherunwanted out-of-band (OOB) emissions. Typically, a linear amplifier,Class-A type, Class-AB type or Class-B is employed to faithfullyreproduce inputs signals and to limit the amplifier output within astrict emissions mask. Linear amplifiers are capable of electrical (DCpower in to RF power out or DC-RF) efficiencies of 50% and greater whenoperated at saturation. However, they are generally not operated at highefficiency due to the need to provide high linearity. For constantenvelope waveforms, linear amplifiers are often operated belowsaturation to provide operation in their linear regime. Time varyingenvelopes present an additional challenge. The general solution is toamplify the peaks of the waveform near saturation, resulting in theaverage power of the waveform being amplified at a level well backed-offfrom saturation. The back-off level, also referred to as output powerback-off (OPBO), determines the electrical efficiency of a linearamplifier.

Modern transmitters for applications such as cellular, personal, andsatellite communications employ digital modulation techniques such asquadrature phase-shift keying (QPSK) in combination with techniques suchas code division multiple access (CDMA). Use of multiple frequencies,simultaneous codes, and/or shaping of the data pulses to mitigateout-of-band emissions from occurring into adjacent channels producestime-varying envelopes. In general these signals, especially thosecreated by multi-carrier signals, have high wide distribution of powerlevels resulting in a large peak-to-average ratio (PAR). Therefore, theoperation of the linear amplifiers in these types of signals is veryinefficient, since the amplifiers must have their supply voltage sizedto handle the large peak voltages even though the signals are muchsmaller a substantial portion of the time. Additionally, the size andcost of the power amplifier is generally proportional to the requiredpeak output power of the amplifier.

Wideband Code Division Multiple Access (WCDMA), Orthogonal FrequencyDivision Multiplexing (OFDM), and multi-carrier versions of both GlobalSystem for Mobile Communication (GSM) and Code Division Multiple Access2000 (CDMA 2000) are wireless standards and application growing in use.Each requires amplification of a waveform with high PAR levels, above 10dB in some cases. The sparse amount of spectrum allocated to terrestrialwireless communication requires that transmissions minimize out-of-band(OOB) emissions to minimize the interference environment. A class “A”linear amplifier used to amplify a waveform with a PAR of 10 dB or moreprovides only 5-10% DC-RF efficiency. The peak output power for theamplifier is sized by the peak waveform. The cost of the amplifierscales with its peak power.

Several other circuit costs including heat sinks and DC-DC powersupplies scale inversely to peak power and dissipated heat (whichresults from the electrical inefficiency). Related base station costs ofAC-DC power supplies, back-up batteries, cooling, and circuit breakersalso scale inversely with efficiency as does the electrical operatingcosts. Clearly, improving DC-RF efficiency is a major cost saver bothfor manufacture and operation. Non-linear classes (e.g., Class C, D, Eand F type amplifiers) of RF power amplifiers switch the RF devices onand off in or near saturation, and are more efficient than linearclasses of operation such as Class-A, Class-AB or Class-B type whichconduct during at least half of the RF cycle and are significantlybacked off from compression. However, non-linear amplifiers can only beemployed with constant envelope signals, such as frequency modulations(FM) and certain forms of phase modulation (PM). Signals with modulatedamplitudes cause severely distorted outputs from these classes ofamplifiers.

Many modern digital communications systems transmit complex waveformsconsisting of multiple carriers, multiple code channels, or othersignals that give rise to large, infrequent peaks in signal power. Thesesignals are costly to transmit in terms of hardware and electricalconsumption. Systems that reduce the size of the peaks withoutintroducing substantial levels of error can operate at lower cost andgreater electrical efficiency; these are clearly desirablecharacteristics.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intendedneither to identify key or critical elements of the invention nordelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

The present invention relates to a communication system having acommunication device that includes a transmitter operative to modify asignal for transmission to reduce peaks associated with the signal. Thesignal can be modified employing signal shaping, signal clipping, signaldecomposition or other techniques to remove peaks associated with thesignal. The communication system can also include a communication devicethat includes a receiver that corrects the modified signal toreconstruct the originally wanted signal.

In one aspect of the present invention, one or more instruction signalsare transmitted to instruct the receiver how to revise the signalmodification enabling substantial peak to average (PAR) reduction. Theinstruction signal or codes can be sent in a parallel or sequentialrelationship with the peak reduced input signal. The instruction signalsor codes indicate to the receiver the nature of the signal modification(e.g., the modification to the modulation constellation) so themodification can be partially or wholly reversed. This allows moreaggressive peak reduction than can be accomplished at the transmitteralone, as errors are repaired at the receiver.

In another aspect of the present invention, the input signal isdecomposed into two or more replica signals of the input signal whosesum is the wanted signal. The replica signals can be added to otherwanted signals, which may be similarly decomposed. Many receivers areequipped to detect time delay signal replicas that occur becauseportions of the received signal have traveled different lengths to thereceiver (the so-called “multi-path” scenario). In this aspect of theinvention the signals will appear at the receiver to be “multi-path”replicas or signals that have propagated over different paths. Thereplica signals can be transmitted with or without an instructionsignal. Receivers designed to recognize and re-combine multi-pathversions of a signal can be employed without an instruction signal.

To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings. These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention will become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic block diagram of communication system inaccordance with an aspect of the present invention.

FIG. 2 illustrates a schematic block diagram of a transmitter employingan instruction signal in accordance with an aspect of the presentinvention.

FIG. 3 illustrates a schematic block diagram of a transmitter employingan instruction code in accordance with an aspect of the presentinvention.

FIG. 4 illustrates a schematic block diagram of a transmitter thatdecomposes a signal into a plurality of replica signals in accordancewith an aspect of the present invention.

FIG. 5 illustrates a schematic block diagram of a transmitter thatdecomposes a signal into a plurality of replica signals in accordancewith another aspect of the present invention.

FIG. 6 illustrates a schematic block diagram of a receiver thatreconstructs a modified input signal employing a construction signal orcode in accordance with another aspect of the present invention.

FIG. 7 illustrates a schematic block diagram of a receiver thatreconstructs a plurality of replica signals into a wanted signal inaccordance with another aspect of the present invention.

FIG. 8 illustrates a methodology for transmitting and receiving a signalin accordance with an aspect of the present invention.

FIG. 9 illustrates a methodology for transmitting and receiving a signalin accordance with another aspect of the present invention.

DETAILED DESCRIPTION OF INVENTION

The present invention relates to a communication system having acommunication device with a transmitter that modifies a signal fortransmission to reduce peaks associated with the signal. Thecommunication system also includes a communication device with areceiver that corrects the modified signal to reconstruct the originallywanted signal. The communication system allows for smaller transmissionpower amplifiers to be employed at the transmitter(s) of thecommunication devices, since the peaks associated with the transmissionsignals have been reduced. Additionally, errors associated with peakreduction are mitigated since the receiver is operative to reconstructthe transmission signal to its originally wanted form.

The present invention reduces peak communication signals to a greaterdegree than previous communication systems, while limiting degradationsto signal error vector magnitude (EVM), receiver bit error rate (BER) orsymbol error rate (SER). Existing techniques to reduce peak-to-averageratios (PAR) are content with the resultant degradations to wantedsignals (characterized by EVM) and out-of-band (OOB) emissions.

FIG. 1 illustrates a communication system 10 in accordance with anaspect of the present invention. The communication system 10 includes afirst communication device 11 having a transmitter 12 and a secondcommunication device 13 having a receiver 14. The first communicationdevice 11 can be a base station and the second communication device 13can be a mobile communication unit (MCU) in a wireless communicationsystem. Alternatively, the second communication device 13 can be a basestation and the first communication device 11 can be a mobilecommunication unit (MCU). It is to be appreciated that the twocommunication device system shown in FIG. 1 is for illustrativepurposes, and that the communication system 10 can include a pluralitycommunication devices each having one or more transmitters andreceivers.

The transmitter 12 includes a signal modifier 16 that receives an inputsignal, for example, from a digital signal processor (DSP) or the like.The signal modifier 16 modifies the input signal to reduce peaksassociated therewith. The signal modifier 16 also can generate aninstruction signal or an instruction code that defines the modificationthat has occurred to the input signal to reduce the peaks associatedwith the input signal. The signal modifier 16 then provides the peakreduced signal and the instruction signal. The instruction signals canbe sent in parallel (e.g., on a separate frequency or on an orthogonalcode) or sequentially with the peak reduced signal. The instructionsignal indicates to the receiver 14 the nature of the modification tothe modulation constellation, so the modification can be partially orwholly reversed. This allows more aggressive peak reduction at thetransmitter 12 as errors are repaired at the receiver 14.

For example, the signal modifier 16 can employ constellation shaping toreduce the peaks and out-of-band (OOB) emissions associated with peakreduction. Constellation shaping is a technique that modifies themodulation constellation of signal to reduce peaks, deliberatelyintroducing errors in the modulation. A bit or symbol transmitted withan erroneous modulation normally cannot be corrected at the receiver andhas an increased probability of resulting in a bit or symbol error. Thepresent invention enables greater peak-to-average ration (PAR) reductionby defining one or more additional signals (instruction signals orinstruction codes) to be transmitted with the peak reduced signal. Theinstruction signals or codes provide the receiver with the necessaryinformation on how to reverse the modifications. Other techniques can beemployed to reduce PAR levels including clipping, and selection ofoptimum signal components (e.g., carrier phase, code selection,frequency, code timing offset).

For communications using code channels (e.g., CDMA, WCDMA, CDMA2000),the addition of a unique code channel(s) is easily adopted for theadditional signals. An allocation of one or a few specific frequenciescan be used for systems using multiple carriers to convey information(e.g., OFDM, Multiple Carrier (MC)-CDMA, Discrete Multi-tone (DMT)). Incertain situations, it may be necessary for the receiver to buffer datafor a short period to extract the additional signals. The secondaryscaling information can be sent in an additional time slot for systemsoperating with Time Division Multiple Access (TDMA). It is also possibleto add a carrier or a polarization code to show the additionalinformation for nominally single carrier systems. It is also possible toadd a code channel to signals that use other techniques.

In another aspect of the invention, the signal modifier 16 separates ordecomposes the input signal into two or more replicas of the inputsignal scaled in amplitude. Recombining the two or more replicas resultsin the original wanted input signal. For example, the signal can bestored briefly (e.g., in digital memory) by the signal modifier anddecomposed into two or more replicas whose sum is the wanted signal.These replicas are added to other wanted signals, which may be similarlydecomposed. The signals will appear at the receiver to be delayed bydifferent lags, the same result as signals reflecting off multiplesurfaces creating “multi-path” replicas. The two or more replicas can becombined with an instruction signal that can be sent in parallel orsequentially. Alternatively, a receiver can be employed that is alreadydesigned, for some formats (e.g., rake receivers for CDMA stylesignals), to recognize and re-combine multi-path versions of a signalwithout the use of an instruction signal.

The signal modifier 16 then provides the modified signal(s) with orwithout the instruction signal to a digital-to-analog converter (DAC)18. The DAC 18 converts the signals from the digital domain to theanalog domain. The analog signals are then provided to an amplifiersystem 20 for amplification. The amplifier system 20 includes a poweramplifier (not shown). The power amplifier can be a linear amplifier(e.g., Class-A, Class-AB, Class-B) or, for some classes of input signal,it can be a non-linear type amplifier (e.g., Class-C, Class-D, Class-E,Class-F) based on desired performance, acceptable efficiency andacceptable OOB emissions. The modified signal (s) with or without theinstruction signal are then transmitted over a wireless link via anantenna 22.

In one aspect of the invention, the DAC 18 is a delta sigma modulatedDAC (e.g., 1-bit delta sigma DAC, multi-bit delta sigma DAC). DeltaSigma modulation is a technique used to generate a coarse estimate of asignal using a small number of quantization levels usually at a veryhigh sampling rate. The small number (two levels for a one-bitquantizer) of discrete levels introduces “quantization” noise into thesystem. The effect of oversampling and the use of an integratorfeedback-loop in delta-sigma modulation are effective in shifting noiseto out-of-band frequencies. The noise shifting properties andintroduction of quantization error enables efficient use of subsequentfiltering stages to remove noise and produce a more preciserepresentation of the input at a much higher frequency. The delta sigmaDACs can be employed to upconvert the input signal directly to radiotransmission frequencies, such that further frequency conversion of thesignals via conventional analog mixers is not required. The radiotransmission frequencies can be in radio frequency (RF) ranges (e.g.,megahertz range) or in microwave frequency ranges (e.g., gigahertzrange).

An antenna 24 captures transmission signals from the transmitter 12, andprovides the transmission signals to a detector/decoder 26. Thedetector/decoder 26 detects the received signals and decodes and/ordemodulates the received signals, which are then provided to a signalcorrector 28. The signal corrector 28 receives the modified outputsignal(s) and any instruction signals or codes that originate from thetransmitter 12 associated with the modified output signal(s). The signalcorrector 28 then reconstructs the signal based on the instructionsignal or code to its original format prior to modification to providethe originally wanted input signal. Alternatively, the signal corrector28 can combine one or more replicas of the input signal into theoriginal wanted input signal based on an instruction signal or code, oremploying multi-path algorithms to reconstruct the original wanted inputsignal prior to modification by the signal modifier 16. The signalcorrector 28 then provides the demodified reconstructed input signal toan analog-to-digital converter (ADC) 30. The ADC 30 converts the analogsignal into a digital signal for further processing by the receiver 14.

FIG. 2 illustrates a schematic block diagram of a transmitter 40 inaccordance with an aspect of the present invention. The transmitter 40includes a signal or constellation shaper 42. The signal shaper 42modifies the modulation constellation or signal to reduce peaks. Avariety of different constellation shaping techniques can be employed toreduce peaks associated with the input signal. The signal shaper 42 iscoupled to a signal generator 44. The signal shaper 42 providesinformation to the signal generator 44 corresponding to modifications ofthe input signal by the signal shaper 42. The signal generator 44 thengenerates an instruction signal or code that informs the receiver thatthe input signal has been modified and information associated with thatmodification. Alternatively, the information associated with thatmodification can reside at the receiver such that a number of knownmodifications are performed at the transmitter and reconstructed at thereceiver based on a defined instruction signal or code. For example, asimple system can employ a minimal instruction signal that is zero mostof the time and takes one or a small number of values coded to a fixedscaling factor when a signal is clipped.

A signal combiner 46 receives the modified or shaped input signal andthe instruction signal or code defining the extent of the modifications(e.g., scaling). The modified or shaped input signal and the instructionsignal are combined for transmission. The combination of the shapedinput signal and the instruction signal can be sent in parallel orsequentially. The instruction signal can be transmitter after or beforethe shaped input signal in a sequential manner. Alternatively, theinstruction signal can be combined with the shaped input signal andtransmitted in parallel. The instruction signal can be modulated intothe shaped signal. For example, the addition of a unique code channel(s) can be employed for the instruction signal for communications usingcode channels (e.g., CDMA, WCDMA, CDMA2000, spread spectrum). Theinstruction signal can be provided in one or a few specific frequenciesin systems employing multiple carriers to convey information (e.g.,OFDM, MC-CDMA, DMT). The instruction signal can be provided in anadditional time slot for systems operating with TDMA.

The signal combiner 46 then provides the shaped signal and instructionsignal to a DAC 48 (e.g., 1-bit delta sigma DAC, multi-bit delta sigmaDAC). The DAC 48 converts the signals from the digital domain to theanalog domain. The analog signals are then provided to an amplifiersystem 50 for amplification. The amplifier system 50 includes a poweramplifier (not shown). The power amplifier can be a linear amplifier(e.g., Class-A, Class-AB, Class-B). For a linear amplifier (class A,A/B, B) there is up to a dB for dB savings in size and cost of theselected amplifier with the peak-to-average ratio (PAR) reduction of theamplification system 50. Thus, if the present invention enables clippingthe signal 3 dB greater than other techniques, the potential costsavings to the amplifier is about 50%. Therefore, the present inventionallows for employment of a power amplifier that is smaller (less power)and operates more efficiently than amplification systems without PARreduction. There is also a significant improvement available in DC-RFefficiency. Efficiency savings reduce board costs and a range of costsassociated with the infrastructure of a transmitter, such as batteriesor backup batteries, AC-DC power converters, and cooling systems.

FIG. 3 illustrates a transmitter 60 in accordance with another aspect ofthe present invention. The transmitter 60 includes a digital signalprocessor (DSP) 62 that generates an input signal for transmission. Theinput signal can be a single carrier or multi-carrier device. The inputsignal is then provided to a modulator 64 that modulates the inputsignal according to a predefined modulation standard (e.g., CDMA,WCDMA). The modulated signal is then provided to a peak detector/clipper66. The peak detector/clipper 66 detects and removes peak signalsassociated with an input signal. The peak detector/clipper 66 provides apeak reduced input signal to a remodulator 70.

The peak detector/clipper 66 also provides information to a signal codegenerator 68. The signal code generator 68 generates a code associatedwith the peak reduction. The signal code generator 68 can be a look uptable and/or algorithm that provides information regarding modificationsto the input signal. The peak reduced input signal and generated codeare provided to the remodulator 70 that can demodulate the peak reducedinput signal and remodulate the peak reduced input signal with theinstruction code embedded therein. Alternatively, the remodulator 70 canprovide an additional modulation that modulates the signal instructioncode into the already modulated peak reduced input signal. Theremodulator 70 can contain a filter to remove unwanted out-of-bandemissions resulting from clipping.

The remodulator 70 then provides the peak reduced input signal with theinstruction code embedded therein to a DAC 72 (e.g., 1-bit delta sigmaDAC, multi-bit delta sigma DAC). The DAC 72 converts the signals fromthe digital domain to the analog domain. The analog signals are thenprovided to an amplifier system 74 for amplification. The amplifiersystem includes a power amplifier that can be a linear amplifier (e.g.,Class-A, Class-AB, Class-B). Employing a linear amplifier (class A, A/B,B) in the transmitter 60 will provide outputs with lower distortions andreduced OOB if the peak signals are reduced.

The techniques of FIGS. 1-3 can result in the PAR level of complexcommunications signals being significantly decreased. For example,reducing a four carrier WCDMA signal from a PAR of 10 dB to a PAR of 5dB is well within reach. This change enables a three times reduction inpower amplifier size and cost and will allow a class A/B amplifiertransmitter to double its DC-RF efficiency from less than 10% to almost20%.

FIG. 4 illustrates a transmitter 80 that generates replica signals inaccordance with another aspect of the present invention. The transmitter80 includes a modulator 82 that modulates an input signal that can be asingle carrier or multi-carrier signal. The modulator 82 modulates theinput signal according to a predefined modulation standard (e.g., CDMA,WCDMA, OFDM, TDMA). The modulated signal is then provided signalsplitter or signal decomposer 84. The signal splitter 84 decomposes thesignal into two or more replicas of the input signal with each replicahaving peak amplitudes that are less than or below the peak amplitudesof the input signal. The two or more replicas are then provided to aparallel-to-serial combiner 86 that sequentially combines the two ormore replicas into a predetermined order for transmission.

The parallel-to-serial combiner 86 then provides the sequentiallyordered two or more replicas to a DAC 88 (e.g., 1-bit delta sigma DAC,multi-bit delta sigma DAC). The DAC 88 converts the signals from thedigital domain to the analog domain. The analog signals are thenprovided to an amplifier system 90 for amplification. The amplifiersystem 90 includes a power amplifier (not shown) that can be a linearamplifier (e.g., Class-A, Class-AB, Class-B). In this aspect of theinvention, a receiver operative to reconstruct signals from multipathsignals such as that employed in CDMA or the like, can be utilizedwithout any or without substantial modifications to the receiver.

FIG. 5 illustrates a transmitter 100 that generates replica signals inaccordance with another aspect of the present invention. The transmitter100 includes a modulator 102 that modulates an input signal that can bea single carrier or multi-carrier signal. The modulator 102 modulatesthe input signal according to a predefined modulation standard (e.g.,CDMA, WCDMA, OFDM, TDMA). The modulated signal is then provided to apeak detector 104. The peak detector 104 detects peak signals associatedwith an input signal and provides information to a signal code generator108. The signal code generator 108 generates a code associated with thepeak reduction. The signal code generator 108 can be a look up tableand/or algorithm that provides information regarding modifications tothe input signal.

The peak detector 104 provides the modulated signal to a signal splitteror signal decomposer 106. The signal splitter 106 decomposes the signalinto two or more replicas of the input signal with each replica havingpeak amplitudes that are less than or below the peak amplitudes of theinput signal. For example, the number of replicas and/or the scaling ofthe replicas can be determined by the peak detector 104. The peakdetector 104 provides this information to the signal code generator 108,which generates a code that provides the necessary information to thereceiver for reconstructing and resealing the two or more replicas intothe wanted signal. The two or more replicas and the signal code are thenprovided to a signal combiner 110 that combines the two or more replicasand the instruction code into a predetermined order for transmission.

The signal combiner 110 then provides the sequentially ordered two ormore replicas to a DAC 112 (e.g., 1-bit delta sigma DAC, multi-bit deltasigma DAC). The DAC 112 converts the signals from the digital domain tothe analog domain. The analog signals are then provided to an amplifiersystem 114 for amplification and transmission as an output signal. Theamplifier system 114 includes a power amplifier (not shown) that can bea linear amplifier (e.g., Class-A, Class-AB, Class-B) biased to handlethe peak reduced replicas, such that operational efficiency of the poweramplifier is improved compared to a transmitter without peak reduction.

FIG. 6 illustrates a receiver 120 in accordance with an aspect of thepresent invention. The receiver 120 is operative to receive transmissionsignal that include peak reduced input signals and instruction signalsthat are received in parallel or sequentially with the peak reducedinput signal. The receiver 120 includes a detector/decoder 122 thatdetects a transmission signal from a transmitter, decodes the detectedtransmission signal and provides that detected transmission signal to ademodulator 124. The demodulator 124 removes the modulation from theinput signal to provide a demodulated input signal to a signal separator126. The signal separator 126 separates the instruction signal from theinput signal. For example, if the instruction code or signal is embeddedinto the input signal, the signal separator 126 removes the instructioncode or signal from the transmission signal and provides the instructioncode or signal to an instruction code or signal resolver 128.Concurrently, the signal separator 126 removes the peak reduced inputsignal from the transmission signal and provides the peak reduced inputsignal to a signal corrector 130.

If the instruction code is a signal that is sequential with the inputsignal, then the signal separator 126 provides the instruction code orsignal portion directly to the instruction code or signal resolver 128,and the peak reduced input signal directly to the signal corrector 130.The instruction information can reside in the instruction code or signalor reside at the receiver where it can be accessed employing theinstruction code or signal. The instruction code or signal resolver 128resolves information associated with the instruction code or signal andprovides the appropriate scaling factor to the signal corrector 130. Thesignal corrector 130 then scales the peak reduced input signal torestore the peak reduced input signal to its original wanted form.

FIG. 7 illustrates a receiver 140 in accordance with another aspect ofthe present invention. The receiver 140 is operative to receivetransmission signal that includes two or more replicas of the inputsignal that may or may not include an instruction signal. The receiverhas a separate signal chain for each replica signal. Each chain has avariable or fixed delay (fixed if the replica delay is fixed by thetransmitter). The receiver can either determine the delays or receiveinstructions on the delays. In the latter case one of the signal chainsis detected and then all the chains are detected using the properinstructions. If the receiver determines the delays then each signalchain is digitized and the delays are varied until the signals aremaximally correlated. Once the proper delays are employed all chains areadded together and then detected/demodulated and decoded as needed.

The receiver 140 includes a detector/decoder 142 that receivestransmission signal that includes two or more replicas of the inputsignal that may or may not include an instruction signal. The two ormore replica signals are then provided to a buffer 144 for temporarystorage and to apply the appropriate delays to each replica. A replicaseparator 145 sequences the retrieval of the replicas from the buffer144 based on their associated delays and provides the two or morereplica signals to a replica adder 146. The replica adder 146 thenrecombines the replica signals into the wanted signal. The wanted signalis then provided to a demodulator 148 that demodulates the wanted signalto provide the original input signal.

In view of the foregoing structural and functional features describedabove, methodologies in accordance with various aspects of the presentinvention will be better appreciated with reference to FIGS. 8-9. While,for purposes of simplicity of explanation, the methodologies of FIGS.8-9 are shown and described as executing serially, it is to beunderstood and appreciated that the present invention is not limited bythe illustrated order, as some aspects could, in accordance with thepresent invention, occur in different orders and/or concurrently withother aspects from that shown and described herein. Moreover, not allillustrated features may be required to implement a methodology inaccordance with an aspect the present invention.

FIG. 8 illustrates a methodology for transmitting a signal in acommunication system in accordance with an aspect of the presentinvention. The methodology begins at 200 where an input signal ismodified to reduced peaks associated with the input signal. The inputsignal can be an input signal that conforms to a variety of differentwireless formats (e.g., WCDMA, OFDM, multi-carrier versions of GSM, CDMA2000). The input signal can be modified by employing signal orconstellation shaping to reduced peaks associated with the input signal.Other techniques can be employed to reduce peak to average (PAR) levelsincluding clipping, and selection of optimum signal components (e.g.,carrier phase, code selection, frequency, code timing offset). Themethodology then proceeds to 210.

At 210, an instruction signal or code is generated. The instructionsignal or code is associated with modifications of the input signal, andincludes instructions or codes for reconstructing the input signal atthe receiver. At 220, the instruction signal or code is combined withthe modified input signal. The instruction signal or code can becombined sequentially (e.g., transmitted in sequence) or in parallel(e.g., instruction signal or code combined within the modulation of theinput signal). For example, the addition of a unique code channel(s) canbe employed for the instruction signal for communications using codechannels (e.g., CDMA, WCDMA, CDMA2000, spread spectrum). The instructionsignal can be provided in one or a few specific frequencies in systemsemploying multiple carriers to convey information (e.g., OFDM, MC-CDMA,DMT). The instruction signal can be provided in an additional time slotfor systems operating with TDMA. At 230, the combined modified inputsignal and instruction signal or code is converted from the digitaldomain to the analog domain, amplified and transmitted as a transmissionsignal over a wireless link. The methodology then proceeds to 240.

At 240, a receiver receives the transmission signal by detecting anddecoding the transmission signal. The transmission signal is thendemodulated to remove the modulation associated therewith. At 250, theinstruction signal and the modified input signal are separated. Theinstruction signal and the modified input signal can be separated byremoving the instruction signal or code embedded in the modified inputsignal or by temporarily storing the instruction signal and the modifiedinput signal in a buffer or the like. The instruction signal is thenemployed to reconstruct the modified input signal into the originallywanted signal at 260. For example, the instruction signal can beemployed to select a scaling factor to scale the modified input signalto its original form at peak areas or to a fixed scale over the entiremodified input signal. It is to be appreciated that a variety of othertechniques can be employed to reconstruct the modified input signal intothe originally wanted signal.

FIG. 9 illustrates a methodology for transmitting a signal in acommunication system in accordance with another aspect of the presentinvention. The methodology begins at 300 where an input signal isdecomposed into a plurality of replica signals. The input signal can bean input signal that conforms to a variety of different wireless formats(e.g., WCDMA, OFDM, multi-carrier versions of GSM, CDMA 2000). At 310,the plurality of replica input signals can be temporarily loaded into abuffer for transmission. At 320, the plurality of replica signals arecombined sequentially with or without an instruction signal to provide atransmission signal comprised of a plurality of sequential replicasignals each having peak signals that are less than the peak signals ofthe original input signal. The methodology then proceeds to 330.

At 330, the plurality of sequential replica signals are converted fromthe digital domain to the analog domain, amplified and transmitted as atransmission signal over a wireless link. The methodology then proceedsto 340. At 340, a receiver receives the transmission signal by reversingthe steps in the transmitter. A separate signal chain is used todigitally process each expected replica signal, for example, one signalchain per replica expected. The receiver either knows a priori ordetermines from the signals (empirically or from an embeddedinstruction) the delays of each replica. In the case of an embeddedinstruction, additional processing must be performed on one version ofthe chain to extract the instruction. Having determined the properdelays, each signal chain is stored into a buffer to apply the correctdelays at 350. At 360, the replica signals are aggregated to provide anaggregated signal and reconsitute the desired signal. The aggregatedsignal is then detected and demodulated at 370.

What has been described above includes exemplary implementations of thepresent invention. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the present invention, but one of ordinary skill in the artwill recognize that many further combinations and permutations of thepresent invention are possible. Accordingly, the present invention isintended to embrace all such alterations, modifications and variationsthat fall within the spirit and scope of the appended claims.

1. A communication device comprising: a signal splitter that decomposesan input signal into a plurality of replica signals, each of theplurality of replica signals being substantial replicas of the inputsignal scaled in amplitude and having a sum that is approximately equalto the input signal, such that each of the plurality of replica signalshas a maximum peak value below the maximum peak value of the inputsignal; a signal combiner that sequentially orders the plurality ofreplica signals for transmission; and a power amplifier that amplifiesthe sequentially ordered plurality of replica signals to provide atransmission signal.
 2. The transmitter of claim 1, the signal combinercombines an instruction signal with the plurality of replica signals,the instruction signal informs a receiver of at least one of the numberof replica signals and an amplitude scaling associated with the replicasignals.
 3. The communication device of claim 2, wherein the instructionsignal is configured as an orthogonal code that is combined with thesequentially ordered plurality of replica signals prior to transmissionfrom the communication device.
 4. The communication device of claim 2,wherein the sequentially ordered plurality of replica signals occupies afirst frequency band and the instruction signal occupies at least oneadditional frequency band, the instruction signal and the sequentiallyordered plurality of replica signals being transmitted substantiallyconcurrently from the communication device.
 5. The communication deviceof claim 2, wherein the instruction signal and the sequentially orderedplurality of replica signals are modulated in a time-division multipleaccess (TDMA) manner prior to transmission.
 6. The communication deviceof claim 1, wherein a known instruction code associated withreconstructing the input signal to its original form prior tomodification resides at a receiver that receives the plurality ofreplica signals, such that the receiver is configured to reconstruct theinput signal to its original form prior to modification based on theknown instruction code.
 7. A communication system comprising: means fordecomposing an input signal into a plurality of replica signals that areeach substantial replicas of the input signal scaled in amplitude andhaving a sum that is approximately equal to the input signal, such thateach of the plurality of replica signals has a maximum peak value belowthe maximum peak value of the input signal; means for sequentiallyordering the plurality of replica signals as a modified input signal;means for generating an instruction signal associated withreconstructing the input signal to its original form prior tomodification; means for transmitting a transmission signal that includesthe modified input signal and the instruction signal transmitted in aparallel relationship, such that the instruction signal is transmittedconcurrently with the modified input signal; means for receiving thetransmission signal; and means for reconstructing the input signal toits original form from the modified input signal prior to modificationemploying the instruction signal that was transmitted in the parallelrelationship with the modified input signal.
 8. The system of claim 7,further comprising means for combining the modified input signal and theinstruction signal into the transmission signal.
 9. The communicationdevice of claim 8, wherein the means for combining comprises means formodulating the instruction signal as an orthogonal code into themodified input signal prior to transmission from the communicationdevice.
 10. The communication device of claim 8, wherein the means forcombining comprises means for modulating the instruction signal into themodified input signal in a time-division multiple access (TDMA) mannerprior to transmission.
 11. The communication device of claim 7, whereinthe means for transmitting is configured to transmit the modified inputsignal at a first frequency band and to transmit the instruction signalat at least one additional frequency band substantially concurrentlyfrom the communication device.
 12. A method of transmitting a signal ina communication system comprising: modifying an input signal into aplurality of replica signals, each of the plurality of replica signalsbeing substantial replicas of the input signal scaled in amplitude andhaving a sum that is approximately equal to the input signal, such thateach of the plurality of replica signals has a peak value below themaximum peak value of the input signal; sequentially ordering theplurality of replica signals into a transmission signal; converting thetransmission signal from the digital domain to the analog domain;amplifying the transmission signal; and transmitting the transmissionsignal.
 13. The method of claim 12, further comprising reconstructingthe plurality of replica signals into the input signal in its originalform prior to modification.
 14. The method of claim 13, furthercomprising modulating an instruction signal as an orthogonal code intothe transmission signal prior to transmission, the instruction signalbeing employed by a receiver to reconstruct the input signal in itsoriginal form prior to modification.
 15. The method of claim 13, furthercomprising transmitting the transmission signal at a first frequencyband and transmitting an instruction signal at at least one additionalfrequency band substantially concurrently, the instruction signal beingemployed by a receiver to reconstruct the input signal in its originalform prior to modification.
 16. The method of claim 13, furthercomprising modulating an instruction signal into the transmission signalin a time-division multiple access (TDMA) manner prior to transmission,the instruction signal being employed by a receiver to reconstruct theinput signal in its original form prior to modification.
 17. The methodof claim 13, wherein reconstructing the plurality of replica signalsinto the input signal comprises reconstructing the plurality of replicasignals into the input signal in its original form prior to modificationbased on a known instruction code associated with reconstructing theinput signal to its original form that resides at a receiver thatreceives the plurality of replica signals.